Tracking Evolution’s Rate through Trilobites

Melanie Hopkins is working to unlock the history of the evolution of animals over vast stretches of geologic time and, for her, the key is trilobites—extinct arthropods that lived for almost 300 million years until 250 million years ago when Earth experienced the largest mass extinction in its history.

“My main work is studying variation within species and how that drives long- term evolution within lineages,” says Dr. Hopkins, who came to the Museum in January 2014 as an assistant curator in the Division of Paleontology after stints of postdoctoral work at The Field Museum of Natural History in Chicago, the Museum für Naturkunde Berlin, and the University of Erlangen-Nuremberg. “One thing that I’m really interested in is when and why rates of evolution are faster in some environments than others.”

Trilobites were incredibly diverse, with more than 20,000 described species. Because their shells were made of the mineral calcite, like those of crabs or clams, trilobites are well represented in the fossil record, preserved in sites all over the world from the United States to China. Moreover, like insects, they molted throughout their lifetimes leaving clues to how they changed during development.

Hopkins’ fieldwork has taken her from Sweden to the deserts of Nevada and Utah. This summer, Hopkins explored several historic fossil beds near Utica. “Trilobite paleontology goes back a long way in New York State,” she says. There is also untold value in mining the Museum’s own trilobite collection of an estimated 400,000 specimens, many from localities no longer accessible.

“Discoveries can actually happen opening up old drawers and finding specimens collected years ago probably for a completely different purpose,” says Hopkins. “Collections can be very useful in answering questions that we hadn’t even thought about when the material was first collected.”